1. Trisetum flavescens (L.) P. Beauv. (yellow oats)

Pl. 136 c, d; Map 553

Plants perennial, with rhizomes lacking, forming loose tufts. Flowering stems 30–90 cm long, erect, sometimes from spreading bases, glabrous or hairy at the nodes. Leaf sheaths rounded on the back, glabrous or the lowermost hairy, the ligule 0.5–2.0 mm long, the margin somewhat uneven and minutely hairy. Leaf blades 2–15 cm long, 2–6 mm wide, flat, glabrous or hairy on the upper surface. Inflorescences 8–20 cm long, relatively dense panicles with short, ascending branches, erect, the main axis glabrous. Spikelets 5.0–7.5 mm long (excluding the awns), somewhat flattened laterally, disarticulating above the glumes, with 2–4 perfect florets. Lower glume 3–4 mm long, narrowly lanceolate, broadest near the base, sharply pointed at the tip, 1‑nerved, keeled, awnless, roughened along the midnerve. Upper glume 5–6 mm long, elliptic‑lanceolate, broadest below the middle, sharply pointed at the tip, 3‑nerved, keeled, awnless, roughened along the midnerve. Lemmas 4–6 mm long, elliptic‑lanceolate, tapered to 2 narrow teeth (notched) at the tip, 3‑ or 5‑nerved, keeled, with an awn 4.5–6.5 mm long attached above the midpoint of the midnerve, this twisted or bent toward the middle, glabrous, often shiny, the base with a tuft of hairs about 1 mm long. Palea slightly shorter than the lemmas, membranous, 2‑nerved. Stamens 3, the anthers 1.5–3.0 mm long. Fruits 2.5–3.0 mm long, narrowly elliptic in outline, brown. 2n=28. May–July.

Introduced, known only from a single historical collection from Jackson County (native of Europe, introduced sporadically in the northern U.S. and adjacent Canada). Habitat unknown, but presumably a moist, disturbed area.

The specimen from Pike County cited by Steyermark (1963) as representing this species is a misdetermined collection of Arrhenatherum elatius, which this species resembles superficially.